1. Field of the Invention
This invention relates to a process for making an aliphatic polycarboxylic acid by the oxidative cleavage of one or more internal carbon--carbon double bonds in an unsaturated aliphatic compound having at least one internal carbon--carbon double bond and at least one terminal methyl group, a terminal carboxyl group and/or a terminal functional group which is oxidizable to a carboxyl group by biooxidation.
2. Description of the Related Art
Aliphatic polycarboxylic acids are versatile chemical intermediates useful as raw materials for the preparation of perfumes, polymers, adhesives and macrolid antibiotics. Aliphatic dicarboxylic acids are an especially important subclass of polycarboxylic acids which includes such commercially important acids as adipic acid, maleic acid, sebacic acid, azelaic acid, dodecanedioic acid, and dimer acid. These dicarboxylic acids are normally made from petroleum-based starting materials except azelaic acid (nonanedioic acid) and sebacic acid (decanedioic acid), which are produced from natural fats and oils in multi-million kilogram quantities.
Azelaic acid is used in the manufacture of urethane elastomers, polyester films and adhesives, plasticizers, and synthetic lubricants. Azelaic acid is the only aliphatic dicarboxylic acid having an odd number of carbon atoms that is available in large quantities.
Azelaic acid is produced commercially by ozonolysis of oleic acid as described in U.S. Pat. No. 2,813,113, the entire contents of which are incorporated herein by reference. In general, the process involves the ozonization of oleic acid to form a mixture of ozonides and subsequent oxidative work-up to form azelaic acid and pelargonic acid in a roughly equimolar amount. A major disadvantage of this process is that each mole of oleic acid produces one mole each of azelaic acid and pelargonic acid, a less desirable by-product of the process.
One way to limit or eliminate the production of pelargonic acid is to use the .omega.-dicarboxylic acid derivative of oleic acid, 9-octadecenedioic acid in place of oleic acid. Since the carbon--carbon double bond in 9-octadecenedioic acid is symmetrical with respect to the terminal carboxylic acid groups, the ozonolysis product of each mole of 9-octadecenedioic acid would produce 2 moles of azelaic acid and no pelargonic acid.
While several chemical routes to the synthesis of long-chain .alpha.,.omega.-dicarboxylic acids such as 9-octadecenedioic acid are available, such methods are complex and usually result in mixtures containing shorter chain lengths. As a result, extensive purification steps are necessary. As an alternative to chemical syntheses, long chain .alpha.,.omega.-dicarboxylic acids such as 9-octadecenedioic acid can be made via fermentation methods such as microbial transformation of the corresponding hydrocarbons such as alkanes or alkenes, fatty acids or esters thereof. One method for producing substantially pure .alpha.,.omega.-dicarboxylic acids in substantially quantitative yield is described in U.S. Pat. No. 5,254,466, the entire contents of which are incorporated herein by reference. This method comprises culturing a C. tropicalis strain wherein both copies of the chromosomal POX5 and each of the POX4A and POX4B genes are disrupted in a culture medium containing a nitrogen source, an organic substrate and a cosubstrate. Since the manufacture of polycarboxylic acids such as azelaic acid in high yield via chemical methods is difficult, it would be desirable to have a method which results in aliphatic polycarboxylic acids in high yield with a minimum of unwanted by-products.
It is therefore, an object of the present invention to provide aliphatic polycarboxylic acids in high yield with a minimum of unwanted by-products. It is also an object of the present invention to provide a specific type of polycarboxylic acids, .alpha.,.omega.-dicarboxylic acids, by means of a combination of biochemical and chemical methods. It is a further object of the present invention to provide azelaic acid in increased yields relative to the existing commercial process by ozonolysis of 9-octadecenedioic acid produced by fermentation of genetically modified C. tropicalis.